[PATCH] mtd: nand: subpage write support for hardware based ECC schemes
Matthieu CASTET
matthieu.castet at parrot.com
Fri Mar 15 09:15:52 EDT 2013
On which controller was it tested ?
The problem is that lot's of controller driver with hw ecc hack the ecc interface.
For example the TI omap driver don't use the data pointer of ecc.calculate but
use the data send on the nand interface.
Matthieu
Gupta, Pekon a écrit :
> From: "Gupta, Pekon" <pekon at ti.com>
>
> This patch adds support for subpage (partial-page) writes when using
> hardware based ECC schemes.
> Advantages:
> (1) reduces storage overhead when using file-systems like UBIFS, which
> store LEB header at page-size granularity.
> (2) allows independent subpage writes, thereby increasing NAND storage
> efficiency for non-page aligned data.
>
> Signed-off-by: Gupta, Pekon <pekon at ti.com>
> ---
> drivers/mtd/nand/nand_base.c | 99 ++++++++++++++++++++++++++++++++++++++------
> include/linux/mtd/nand.h | 8 +++-
> 2 files changed, 92 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 4321415..5138b6b 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -1127,7 +1127,7 @@ static int nand_read_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
> }
>
> /**
> - * nand_read_subpage - [REPLACEABLE] software ECC based sub-page read function
> + * nand_read_subpage - [REPLACEABLE] ECC based sub-page read function
> * @mtd: mtd info structure
> * @chip: nand chip info structure
> * @data_offs: offset of requested data within the page
> @@ -1979,6 +1979,67 @@ static int nand_write_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip,
> return 0;
> }
>
> +
> +/**
> + * nand_write_subpage_hwecc - [REPLACABLE] hardware ECC based subpage write
> + * @mtd: mtd info structure
> + * @chip: nand chip info structure
> + * @column: column address of subpage within the page
> + * @data_len: data length
> + * @oob_required: must write chip->oob_poi to OOB
> + */
> +static int nand_write_subpage_hwecc(struct mtd_info *mtd,
> + struct nand_chip *chip, uint32_t offset,
> + uint32_t data_len, const uint8_t *data_buf,
> + int oob_required)
> +{
> + uint8_t *oob_buf = chip->oob_poi;
> + uint8_t *ecc_calc = chip->buffers->ecccalc;
> + int ecc_size = chip->ecc.size;
> + int ecc_bytes = chip->ecc.bytes;
> + int ecc_steps = chip->ecc.steps;
> + uint32_t *eccpos = chip->ecc.layout->eccpos;
> + uint32_t start_step = offset / ecc_size;
> + uint32_t end_step = (offset + data_len - 1) / ecc_size;
> + int oob_bytes = mtd->oobsize / ecc_steps;
> + int step, i;
> +
> + for (step = 0; step < ecc_steps; step++) {
> + /* configure controller for WRITE access */
> + chip->ecc.hwctl(mtd, NAND_ECC_WRITE);
> +
> + /* write data (untouched subpages already masked by 0xFF) */
> + chip->write_buf(mtd, data_buf, ecc_size);
> +
> + /* mask ECC of un-touched subpages by padding 0xFF */
> + if ((step < start_step) || (step > end_step))
> + memset(ecc_calc, 0xff, ecc_bytes);
> + else
> + chip->ecc.calculate(mtd, data_buf, ecc_calc);
> +
> + /* mask OOB of un-touched subpages by padding 0xFF */
> + /* if oob_required, preserve OOB metadata of written subpage */
> + if (!oob_required || (step < start_step) || (step > end_step))
> + memset(oob_buf, 0xff, oob_bytes);
> +
> + data_buf += ecc_size;
> + ecc_calc += ecc_bytes;
> + oob_buf += oob_bytes;
> + }
> +
> + /* copy calculated ECC for whole page to chip->buffer->oob */
> + /* this include masked-value(0xFF) for unwritten subpages */
> + ecc_calc = chip->buffers->ecccalc;
> + for (i = 0; i < chip->ecc.total; i++)
> + chip->oob_poi[eccpos[i]] = ecc_calc[i];
> +
> + /* write OOB buffer to NAND device */
> + chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);
> +
> + return 0;
> +}
> +
> +
> /**
> * nand_write_page_syndrome - [REPLACEABLE] hardware ECC syndrome based page write
> * @mtd: mtd info structure
> @@ -2031,6 +2092,8 @@ static int nand_write_page_syndrome(struct mtd_info *mtd,
> * nand_write_page - [REPLACEABLE] write one page
> * @mtd: MTD device structure
> * @chip: NAND chip descriptor
> + * @offset: address offset within the page
> + * @data_len: length of actual data to be written
> * @buf: the data to write
> * @oob_required: must write chip->oob_poi to OOB
> * @page: page number to write
> @@ -2038,15 +2101,25 @@ static int nand_write_page_syndrome(struct mtd_info *mtd,
> * @raw: use _raw version of write_page
> */
> static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
> - const uint8_t *buf, int oob_required, int page,
> - int cached, int raw)
> + uint32_t offset, int data_len, const uint8_t *buf,
> + int oob_required, int page, int cached, int raw)
> {
> - int status;
> + int status, subpage;
> +
> + if (!(chip->options & NAND_NO_SUBPAGE_WRITE) &&
> + chip->ecc.write_subpage)
> + subpage = offset || (data_len < mtd->writesize);
> + else
> + subpage = 0;
>
> chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);
>
> if (unlikely(raw))
> - status = chip->ecc.write_page_raw(mtd, chip, buf, oob_required);
> + status = chip->ecc.write_page_raw(mtd, chip, buf,
> + oob_required);
> + else if (subpage)
> + status = chip->ecc.write_subpage(mtd, chip, offset, data_len,
> + buf, oob_required);
> else
> status = chip->ecc.write_page(mtd, chip, buf, oob_required);
>
> @@ -2160,7 +2233,7 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
>
> uint8_t *oob = ops->oobbuf;
> uint8_t *buf = ops->datbuf;
> - int ret, subpage;
> + int ret;
> int oob_required = oob ? 1 : 0;
>
> ops->retlen = 0;
> @@ -2175,10 +2248,6 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
> }
>
> column = to & (mtd->writesize - 1);
> - subpage = column || (writelen & (mtd->writesize - 1));
> -
> - if (subpage && oob)
> - return -EINVAL;
>
> chipnr = (int)(to >> chip->chip_shift);
> chip->select_chip(mtd, chipnr);
> @@ -2227,9 +2296,9 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
> /* We still need to erase leftover OOB data */
> memset(chip->oob_poi, 0xff, mtd->oobsize);
> }
> -
> - ret = chip->write_page(mtd, chip, wbuf, oob_required, page,
> - cached, (ops->mode == MTD_OPS_RAW));
> + ret = chip->write_page(mtd, chip, column, bytes, wbuf,
> + oob_required, page, cached,
> + (ops->mode == MTD_OPS_RAW));
> if (ret)
> break;
>
> @@ -3458,6 +3527,10 @@ int nand_scan_tail(struct mtd_info *mtd)
> chip->ecc.read_oob = nand_read_oob_std;
> if (!chip->ecc.write_oob)
> chip->ecc.write_oob = nand_write_oob_std;
> + if (!chip->ecc.read_subpage)
> + chip->ecc.read_subpage = nand_read_subpage;
> + if (!chip->ecc.write_subpage)
> + chip->ecc.write_subpage = nand_write_subpage_hwecc;
>
> case NAND_ECC_HW_SYNDROME:
> if ((!chip->ecc.calculate || !chip->ecc.correct ||
> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> index 7ccb3c5..7d81403f 100644
> --- a/include/linux/mtd/nand.h
> +++ b/include/linux/mtd/nand.h
> @@ -354,6 +354,7 @@ struct nand_hw_control {
> * any single ECC step, 0 if bitflips uncorrectable, -EIO hw error
> * @read_subpage: function to read parts of the page covered by ECC;
> * returns same as read_page()
> + * @write_subpage: function to write parts of the page covered by ECC.
> * @write_page: function to write a page according to the ECC generator
> * requirements.
> * @write_oob_raw: function to write chip OOB data without ECC
> @@ -385,6 +386,9 @@ struct nand_ecc_ctrl {
> uint8_t *buf, int oob_required, int page);
> int (*read_subpage)(struct mtd_info *mtd, struct nand_chip *chip,
> uint32_t offs, uint32_t len, uint8_t *buf);
> + int (*write_subpage)(struct mtd_info *mtd, struct nand_chip *chip,
> + uint32_t offset, uint32_t data_len,
> + const uint8_t *data_buf, int oob_required);
> int (*write_page)(struct mtd_info *mtd, struct nand_chip *chip,
> const uint8_t *buf, int oob_required);
> int (*write_oob_raw)(struct mtd_info *mtd, struct nand_chip *chip,
> @@ -520,8 +524,8 @@ struct nand_chip {
> int (*errstat)(struct mtd_info *mtd, struct nand_chip *this, int state,
> int status, int page);
> int (*write_page)(struct mtd_info *mtd, struct nand_chip *chip,
> - const uint8_t *buf, int oob_required, int page,
> - int cached, int raw);
> + uint32_t offset, int data_len, const uint8_t *buf,
> + int oob_required, int page, int cached, int raw);
> int (*onfi_set_features)(struct mtd_info *mtd, struct nand_chip *chip,
> int feature_addr, uint8_t *subfeature_para);
> int (*onfi_get_features)(struct mtd_info *mtd, struct nand_chip *chip,
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